Inorganic oxidizer blasting slurry containing smokeless powder and aluminum



United States Patent 3 331 717 INORGANIC OXIDiZEli BLASTING SLURRY CONTAINING SMOKELESS POWDER AND ALUMINUM Melvin A. Cook and Douglas H. Pack, Salt l lake City,

Utah, and John N. Gardner, Santa Cruz, Calrfl, assignors to Intermountain Researcll1l& Engineering Coman Inc. a corporation of Uta i 10 l havving. Filed Apr. 13, 1965, Ser. No. 447,897 9 Claims. (Cl. 14938) This application is a continuation-in-part of application Ser. No. 67,177 filed Nov. 4, 1960, now abandoned.

This invention relates to explosive compositions, and more particularly, to blasting agents in slurry form based on large proportions of inorganic nitrates or chlorates, or mixtures thereof, containing smokeless powder, aluminum, and a liquid. By such blasting agents reference is made particularly to relatively insensitive explosive compositions of high power which ordinarily cannot be detonated by means of a simple commercial blasting cap or Primacord initiator but which requires a strong, high pressure booster, such as cast 50/50 pentilite in appreciable mass, I

for example, to detonate it reliably.

A typical blasting agent is one which contains 40 or 50 percent, or more, of a powerful oxidizer and enough liquid to make the entire composition plastic or flowable. Such compositions are now well known in the art, havmg been described in U.S. Patent No. 2,930,685 and in U.S. Reissue Patent No. 25,695. The principal novelty ofthe present invention lies in combining with thebasrc oxidizer (such as ammonium nitrate, or sodium nitrate, or m xtures thereof, or blends of one or more such nitrates w1th inorganic chlorates and the like) an effective and novel sensitizer in the form of a combination of smokeless powder and an effective and powerful metal in subdivided form. Aluminum is the preferred metal, although magnesium sometimes may be used.

Smokeless powder is a well known explosive, being the basic propellant commonly used for artillery shells, small arms ammunition, and the like. It is available in several forms, commonly referred to as single base, double base, and triple base, for example. It is basically a cellulose nitrate but may contain nitroglycerine and other ingredients. While its uniformity and stability have been improved over the years, smokeless powder, which is made and stored in large quantities, e.-g., for military use, tends to deteriorate somewhat on aging. As a consequence, smokeless powder, as stored in ordnance depots, etc., may ultimately become unsafe or unreliable for use in its military applications just named. As a result, much smokeless powder, e.g., from unused ammunition, which otherwise usually would be too expensive for consideration for use in commercial blasting agents, may become available in quantity at times as surplus material. On the other hand, it frequently will still serve very well for the purposes of this invention.

Under these circumstances, smokeless powder suitable for use in the present invention may be obtained at such low cost, at times, as to be of considerable interest for use in quantity in commercial explosives. It is also true that in some forms smokeless powder may be reprocessed and made available for its original purposes, e.g., in ammunition and as a military propellant. Reprocessing of some powders to give products of the desired particle size for use in ammunition is usually expensive and difficult. Reprocessing, nevertheless, is often a practical means of making available for commercial use the coarser grained smokeless powders obtained as surplus from military stocks. It has been found, according to the present invention, that either fresh or aged smokeless powder, which may be either in its original form or may be ground from 3,331,717 Patented July 18, 1967 the larger particle sizes into products of smaller and more appropriate or useful particle size, is suitable for use in commercial blasting. Thus, this surplus military material no longer suitable for its original purpose may be economically and efiiciently utilized insafe and dependable blasting agents, according to this invention, especially when combined with aluminum. The combination of a small proportion of particulate metallic aluminum with such smokeless powder, either single, double, or triple base, is a particularly eflicient sensitizer for high inorganic nitrate slurries.

A smokeless powder of the single-base type has the following typical composition by weight:

Percent Nitrocellulose (11-14% N) Dinitrotoluene l0 Dibutyl phthalate 4 Diphenylamine 1 Typical smokeless powders of the double-base type Thus, the composition of smokeless powder may vary somewhat; not only may dinitrotoluene and nitroglycerine be present but also different plasticizers, stabilizers and oxidants may be utilized. The term smokeless powder as used herein refers, as previously suggested, either to single-base types containing roughly 85% nitrocellulose by weight, to double-base types containing roughly 94% of a combination of nitrocellulose plus nitroglycerine, or to triple-base powders. For safety reasons, it is often preferable to use the single-base types, although the doublebase and triple-base types generally may also be used in formulations, according to this invention.

The blasting agents of this invention are relatively safe slurries. They may be used in blasting operations in boreholes that are wet, waterfilled, or dry, and of either large or small diameter. The slurries of the invention are relatively insensitive to shock, impact, friction and heat, while being dependably detonable by relatively small boosters of high brisance material such as cast 50/ 50 pentolite, or cast Composition B.

The blasting compositions of the invention, in their preferred form, comprise aqueous slurries or slurries of other liquid component, and of various different particulate solids. In general, said solids may comprise about 10 to about 85 percent by weight of smokeless powder, preferably below 50% in most cases, about to 15 percent by Weight of a solid oxidant, preferably ammonium nitrate, although at least part of the ammonium nitrate may be replaced by sodium nitrate or by an inorganic chlorate or perchlorate, and 0.2 to 20 percent by weight of particulate aluminum. The liquid content, usually aqueous, of the slurry is from about 7 to about 25 percent by weight. Glycols, monohydric alcohols and various watercompatible energy-giving liquids may be substituted in whole or in part.

The smokeless powder utilized in this invention may be of grain size ranging from small cylindrical particles of about 0.04" in diameter by 0.1" long to relatively large particles, e.g., of about 0.3" diameter by about 0.8" long. Alternatively, ground smokeless powders, including those of particle size less than about 4 mesh, may be utilized. The extruded cylinders of smokeless powder, in its conventional particulate form for use in ammunition, especially those in the larger size range, usually have holes running therethrough. These holes, if plural, normally are arranged generally in a pattern symmetrically about the axis of the cylindrical particle. The smallest size grains may have no perforations at all or may have only one axial hole in the extruded grain. It has been found that the smaller sizes (0.04" diameter by 0.1" long) tend to produce the most sensitive slurries whereas, for grain sizes larger than about 0.3" diameter by 0.8 long, a successful slurry blasting composition may require the addition of auxiliary sensitizers. With aluminum present, other sensitizers are not usually needed but explosive sensitizers such as coarse grained TNT, or TNT-containing compositions (of 4-20 mesh, preferably) may be added in addition to the aluminum if the smokeless powder is of the single-base type and of large grain size. However, smokeless powders of larger particle sizes generally may be used without auxiliary sensitizers, other than aluminum, especially where the aluminum is of the highly active type, i.e., fine-grained and/or with surface phenomena conducive to high explosive sensitivity. This is especially true if the more sensitive double-base or triple base types of smokeless powder are utilized.

The oxidant used in the slurry may be, and preferably is, ammonium nitrate. However, as noted above, sodium nitrate, sodium chlorate or perchlorate, ammonium perchlorate or other nitrates, chlorates and perchlorates, and mixtures thereof may be used to replace at least a part of the ammonium nitrate. Generally, some ammonium nitrate will be used, preferably at least half of the total oxidants. It has been found that the chlorates named, long considered particularly hazardous in many situations, may be utilized, particularly in aqueous slurries of this present invention, with relative safety and with good resistance to accidental ignition or detonation, well within the limits usually required for commercial blasting agents. The particle size of the oxidant generally is not critical. As a rule, relatively fine-grained oxidants are utilized, but ammonium nitrate prills can be used and any particle size less than about 6 mesh is satisfactory for the compositions of this invention.

In many, and probably in most applications it is desirable to thicken the slurry. This is done in ways now well known, e.g., with a hydrophilic colloid such as starch, wheat flour, guar gum, and especially with guar gum cross-linked with borax or equivalent, and the like. A water-soluble polyacrylamide known as Superfloc 16 also has been found to be particularly useful for this purpose, especially when sodium chlorate is used in the oxidant. In this case one employs, for example, alum for cross-linking the thickening agent, thereby substantially increasing its effect as a thickener. Where utilized, such thickeners are present in an amount of 0.01 to 2 percent by weight of the slurry. The thickener is used so that the explosive composition will set up quickly, at least to some extent, and become more resistant to outside water and more stable against separation of some of the solid components by gravity. This resistance to water leaching is important when the composition is used in the presence of substantial quantities of ground water.

Other and non-explosive fuels also may be added to the slurry, e.g., to regulate oxygen balance, if desired, in addition to the aluminum. Such fuels include powdered coal, fuel oil, tall oil, ethylene glycol, and the 'like. Starches and/or sugars, i.e., carbohydrates may be used. From a fraction of one percent to as much as ten percent of the slurry may comprise such fuels, if desired.

The amount of liquid, usually water or water plus an oxygenated hydrocarbon such as alcohol, glycol, etc., preferably is employed in the range of 7 to 25 percent by weight of the total slurry, depending to some extent on the amount of solid oxidant which is soluble in the liquid of the composition. Preferably, the amount of water or other liquid is just sufficient to provide an easily pourable slurry. This usually requires liquid in the range of about 10 to percent by weight of the total slurry. Proportions will vary, however, with variations in other components. The density of the whole slurry is usually within the range of about 1.20 to 1.9 g./cc., the lower density limit being obtained with low density oxidants such as ammonium nitrate, and the high density limit resulting from the use of higher density oxidants such as sodium chlorate, e.g., in amounts in excess of 50 percent. The preferred density range is between about 1.35 to 1.75 grams per cc.

The slurry explosives usually preferred for the invention are especially those based mainly on ammonium nitrate, or mixtures of ammonium nitrate and sodium nitrate, along with the smokeless powder and aluminum. Such inorganic nitrates usually form at least 20% and preferably at least 50% by weight of the total composition. The water or other liquid is preferably insufficient to dissolve all of the inorganic nitrate salts. Hence, particulate and undissolved ammonium nitrate, with or without sodium nitrate, is usually present in substantial proportions.

Compositions including chlorates with smokeless powder preferably also include at least some ammonium nitrate. Compositions based on high proportions of sodium chlorate, along with smokeless powder and aluminum, provide high maximum available energy. Because of their relatively high density, the bulk strength, i.e., available energy per unit volume, i very high. The chlorates, if used alone, may tend to be somewhat more hazardous than the high ammonium nitrate materials. It has been discovered in the present invention, however, that the higher sodium chlorate slurries of this invention do have higher performance sensitivity (ability to perform satisfactorily in the borehole) than prior art slurry blasting agents of the same coarse explosive sensitizer content and particle size, as determined by tests involving conventional unconfined charges, minimum booster and critical diameter propagation properties. This higher performance is sometimes highly advantageous and may outweigh the tendency to greater hazards with chlorate type materials.

The blasting agents of this invention, generally speaking, may be dependably and most economically detonated by boosters of high brisance, such as cast pentolite, cast or pressed explosives based on RDX, and the like. Multiple stage boosters of the types described in U.S. Patents Nos. 3,037,452 and 3,037,453 are particularly preferred.

Most of the slurry explosives of the invention may be safely manufactured, stored and shipped. Hence, many of them may be prepared in a processing plant and transported to the blasting site. Desirably, however, the slurries can be prepared on or near the site of use. This is particularly advantageous in blasting in dry boreholes. All the individual components are safe to handle under ordinary conditions. For maximum safety they need not be combined to make up the explosive until just before placement in the borehole.

The following examples will illustrate the desirable properties of the smokeless powder-aluminum sensitized blasting agents of this invention. All components are given by weight. The smokeless powder utilized in these examples had approximately the composition given above for a typical single-base type. Some compositions without aluminum are shown first.

The above compositions were fired utilizing gram cast pentolite boosters initiated by Primacord. It will be noted that with this fine-grained smokeless powder and no aluminum, a relatively sensitive composition was obtained.

strength of 1.15 had Composition A. A product of density p: 1.45, of Composition B, had a seismic strength of 1.05.

Percentages are by weight.

Example II Composition Size Diame- Length, A B C D ter, Inch Inch 0.04 0.1 50.0 25 Smokeless Powder (20 mm. cartridge type) g8 50.

Sodium Chlorate (20 mesh) Fuel (coal, oil, etc.) Water Thickener Density (g./ec.) Critical diameter (inches) The above slurries were fired with 160 gram cast pentolite boosters. In the Examples A, B and C, the thickener was Superfloc 16, a water-soluble polyacrylamide, crosslinked with alum. The pronounced drop in sensitivity, as measured by critical diameter, with increasing grain size in the smokeless powder, is noted.

Example III Composition A I B C Smokeless Power (1/32" x 3/32) 32 20 30 Ammonium Nitrate (-10 mesh) 68 78 70 Water 9. 5 24 Fuel Oil 2. 5 Thickener 1. 5 Density (g./cc.) 1. 5 1. 45 1. 35 Critical diameter 1. 25 5 5 The above blasting agents were fired with 160 gram cast pentolite boosters. In Example III(C) the thickener was guar gum cross-linked with borax in ethylene glycol, added as a syrup.

The following tables show preferred compositions containing aluminum, according to the present invention. AN refers to ammonium nitrate, AL to aluminum, SP to single-base smokeless powder, HSSP to triple-base or high strength smokeless powder (approximate composition 55% nitroguanidine, %nitroglycerine and nitrocellu lose). Density p is shown in grams per cubic centimeter. The thickener may be either flour, starch or guar gum, the latter usually being preferred. SN is sodium nitrate and E6 is ethylene glycol. Critical diameter (unconfined) d is shown in inches. SS, seismic strength, is related to a value 1.0 for ammonium nitrate prills with 6% fuel oil, as a comparison of relative blasting power. The stabilizer is needed to inhibit reaction between water and fine particled aluminum. See US. Patent 3,113,059 for a preferred-type stabilizer.

A product having a density p of 1.5 and a seismic A, Percent B, Percent AN 46. 3 51. 3 AL 15 8 HSSP- 20 18 5 H2O 13 13 Guar Guru 0. 5 0.5 Inhibitor 0. 2 0. 2 SulfuL. 1.0 2.0 N 4. 0 7. 0 EG 1.0 1.0 (1,, inches... 5 5 30 Product A was made up as a batch in a conventional concrete mixer. The ammonium nitrate, sodium nitrate, and the stabilizer (an ammonium or sodium phosphate) were first poured in as warm aqueous solutions. Thereafter, the granular smokeless powder and fine-particle aluminum and sulfur were added while mixing and the batch allowed to aerate. Finally, the ethylene glycol and the guar gun dissolved or dispersed therein were added as a thick syrup. The mixture soon thickened up enough to prevent gravity separation of the smokeless powder granules and the product was then packaged in plastic tubes or bags.

Samples were detonated successfully in S-inch columns, using 50 gram pentolite detonators.

The warm solution may or may not contain particulate undissolved ammonium nitrate or sodium nitrate, but on cooling it generally does, i.e., it usually will be more than saturated at normal temperatures.

A most significant fact concerning aluminum-smokeless powder combinations as sensitizers for slurry explosives is that the use of aluminum reduces phenomenally the minimum smokeless powder requirement to attain a critical level of sensitivity. This permits one to operate at much lower percentages of smokeless powder than would be possible without aluminum. At the same time, as already mentioned, the strength of the smokeless powdersensitized slurry is markedly increased by the use of aluminum.

For example, depending on the types of smokeless powder used, one requires at least 20%, usually at least 25% and sometimes even 30%, smokeless powder to sensitize adequately an ammonium nitrate-based slurry used in 4" and greater diameters if only smokeless powder is used as the sensitizer. However, by the use of only about 5% aluminum, for example, the smokeless powder requirement for adequate sensitivity in charges of diameter 4" or greater may be reduced to as low as 5% using a suitably granulated aluminum. The aluminum is preferably finely divided, i.e., below about mesh, and is well distributed. The slurry is preferably thickened also to minimize separation of the solid constitutents.

The aluminum smokeless powder compositions are found to be much more accurately controllable as to sensitivity than compositions lacking aluminum. The

combination of aluminum and smokeless powder, with an aqueous slurry of ammonium nitrate, thickened to prevent gravity separation of the solids, is a particularly inexpensive, powerful and accurately controllable material.

While the invention has been described in terms of certain examples, they are to be considered illustrative and not limiting and it is intended to cover all modifications and embodiments that fall within the spirit and scope of the appended claims.

What is claimed is:

1. A slurry blasting agent having a density of 1.20 to 1.95 grams/cc. which is stable against gravitational separation of suspended solids and resistant to leaching by external water, which agent comprises an aqueous suspending liquid including to 20% by weight of Water, based on the total composition, an inorganic normally solid oxidizer selected from the group which consists of ammonium nitrate, sodium nitrate, sodium chlorates and perchlora-tes, ammonium perchlorates, and mixtures thereof, a small amount of a colloidal thickener for said water, to 40% by weight of granular smokeless powder of at least 0.0 particle diameter, and finely divided particulate metallic aluminum in proportions between 1 and 10% by weight.

2. Blasting agent according to claim 1 which contains 0.01 to 0.05% of a stabilizer to substantially prevent aluminum-water reaction.

3. Blasting agent according to claim 1 wherein the aqueous liquid includes a small amount of a glycol.

4. The blasting agent set forth in claim 1, wherein the thickener includes about 0.01 to 2 percent by weight of a hydrophilic colloid.

5. The blasting agent set forth in claim 1, wherein said oxidant is primarily ammonium nitrate.

6. The blasting agent set forth in claim 1, wherein said oxidant comprises sodium nitrate.

7. Composition according to claim 1 which also contains ethylene glycol in proportions of 7 to 25% that of the water.

8. Composition according to claim 1 which also contains 1 to 6% of sulfur.

9. A slurry type blasting composition consisting essentially of a pourable slurry of solids in aqueous liquid and having a consistency stable against substantial segregation of components by gravity and resistant to leaching by external water, said solids comprising 5 to by weight, based on the total slurry, of smokeless powder particles of size ranging between 0.04" and 0.3" in diameter and 0.1" and 0.8 in length, 1 to 10% of aluminum particles, said slurry containing a substantially oxygen balancing amount of a normally solid inorganic oxidant comprising ammonium nitrate, said oxidant being at least partly dissolved in said aqueous liquid, a stabilizer for substantially preventing wateraluminum reaction under storage conditions and an amount of thickening agent sufiioient to substantially thicken said liquid.

References Cited UNITED STATES PATENTS 2,945,751 7/1960 ONeill 14938 X 3,113,059 12/1963 Ursenbach et a1. 14941 3,147,163 9/1964 Griffith et al. 14941 X 3,235,425 2/1966 Clemmens et al. 149-53 X CARL D. QUARFORTH, Primary Examiner. BENJAMIN R. PADGETT, Examiner.

S. J. LECHERT, JR., Assistant Examiner. 

1. A SLURRY BLASTING AGENT HAVING A DENSITY OF 1.20 TO 1.95 GRAMS/CC. WHICH IS STABLE AGAINST GRAVITATIONAL SEPARATION OF SUSPENDED SOLIDS AND RESISTANT TO LEACHING BY EXTERNAL WATER, WHICH AGENT COMPRISES AN AQUEOUS SUSPENDING LIQUID INCLUING 10 TO 20% BY WEIGHT OF WATER, BASED ON THE TOTA COMPOSITION, AN INORGANIC NORMALLY SOLID OXIDIZER SELECTED FROM THE GROUP WHICH CONSISTS OF AMMONIUM NITRATE, SODIUM NITRATE, SODIUM CHLORATES AND PERCHLORATES, AMMONIUM ERCHLORATES, AND MIXTURES THEREOF, A SMALL AMOUNT OF A COLLOIDAL THICKENER FOR SAID WATER, 15 TO 40% BY WEIGHT OF GRANULAR SMOKELESS POWDER OF AT LEAST 0.04" PARTICLE DIAMETER, AND FINELY DIVIDED PARTICULATE METALLIC ALUMINUM IN PROPORTIONS BETWEEN 1 AND 10% BY WEIGHT. 